gha: Switch to kubeadm for run-k8s-tests-on-zvsi

Last November, SUSE discontinued support for s390x, leaving k3s
on this platform stuck at k8s version 1.28, while upstream k8s
has since reached 1.31. Fortunately, kubeadm allows us to create
a 1.30 Kubernetes cluster on s390x.
This commit switches the KUBERNETES option from k3s to kubeadm
for s390x and removes a dedicated cluster creation step.
Now, cluster setup and teardown occur in ACTIONS_RUNNER_HOOK_JOB_{STARTED,COMPLETED}.

Signed-off-by: Hyounggyu Choi <Hyounggyu.Choi@ibm.com>

.github/workflows/run-k8s-tests-on-zvsi.yaml

@@ -36,7 +36,7 @@ jobs:
           - qemu-runtime-rs
           - qemu-coco-dev
         k8s:
-          - k3s
+          - kubeadm
         include:
           - snapshotter: devmapper
             pull-type: default
@@ -97,9 +97,6 @@ jobs:
           echo "KBS_INGRESS=nodeport" >> $GITHUB_ENV
         if: ${{ matrix.vmm == 'qemu-coco-dev' }}
 
-      - name: Deploy ${{ matrix.k8s }}
-        run: bash tests/integration/kubernetes/gha-run.sh deploy-k8s
-
       # qemu-runtime-rs only works with overlayfs
       # See: https://github.com/kata-containers/kata-containers/issues/10066
       - name: Configure the ${{ matrix.snapshotter }} snapshotter